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Full text of "The manufacture and properties of iron and steel"

484                                    THE IRON" INDUSTKY.
The feature of this district is the deposit of ore at Cornwall, near Lebanon. The hills in which the ore occurs were held in private hands from 1732 down to 1894; but in that year the Lacka-wanna Iron and Steel Company acquired a one-third interest and in 1901 The Pennsylvania Steel Company bought a still larger share. This mine has been worked since 1740, and up to the end of 1904 had produced 18,000,000 tons of ore, which was more than had been obtained from any other one mine in the United States, and up to 1893 it was the largest single producer. The Port Henry mines in New York have raised two-thirds as much, having been operated since 1804. The present rate of production at Cornwall is 750,000 tons per year, and there is no other mine north of Alabama and east of Michigan which raised as much as 110,000 tons in 1903. The ore is a magnetite, low in phosphorus, but intimately, mixed with clayey.matter, and the deposit is permeated by streaks of copper-bearing sulphides. Some streaks can be separated, but there is such a mixing of the minerals that the ore as mined contains a considerable quantity of both of these elements. The copper varies, but the pig-iron from selected ore will contain about 0.60 per cent, of copper, while the run of the mine will give a somewhat higher proportion.
The sulphur will run from 2 to 2.50 per cent., and roasting is always practiced, about half the sulphur being removed in this way. The run of the mine contains from 40 to 42 per cent, of iron and 20 per cent, of silica, with a small proportion of lime and magnesia. The roasted ore contains from 1 to 1.25 per cent, of sulphur, and 40 per cent, of iron, so that in order to make 100 pounds of pig-iron, the. ore will carry from 2.5 to 3 pounds of sulphur into the furnace. There" will also he needed about 1.5 tons of coke carrying 1 per cent, of sulphur, or 1.5 pounds per 100 pounds of iron, and there will, therefore, be from 4 to 4.5 pounds of sulphur added per 100 pounds of iron. In ordinary blast-furnace practice, where the ore has no sulphur and the fuel ratio is one to one, the total sulphur per 100 pounds of iron will be 1 pound, so that in using Cornwall ore the sulphur in the burden is from four to five times as much as in ordinary practice.
It is, therefore, necessary to run the Cornwall furnaces extremely hot, in order to make good iron, and, as a consequence, the-iron is high in silicon, usually containing over 2 per cent, and frequently